Knee prosthesis

ABSTRACT

A prosthetic device for the knee comprises a block which may be cast as a rigid, urethane member which closely resembles the appearance of the knee, and which includes an integrally formed resilient knee pad to serve as a shock absorber, to reduce pant leg wear, and to simplify the fabrication technique. The device is formed in a mold cavity by first pouring the knee pad material, such as pigmented resilient polyurethane, in the lower end thereof and allowing it to set. Rigid polyurethane material is then added and allowed to expand and fill the mold cavity, and to cure into a rigid state. The block is attachable to the lower end of an upper leg or femural prosthesis. A pigmented resin is used to form a laminate over the femural section and knee, using nylon and fiberglass as the matrix for the resin. The laminate fits flush with an annular shoulder extending from the knee pad. A knee prosthesis having a lightweight unitary construction, smooth continuous surface, realistic flesh tone exterior, and a similarly flesh-toned resilient knee pad is thus formed. In another embodiment of the insertion, the knee block includes a larger link cavity for attachment to a lower leg prosthesis, and the knee pad includes a flap portion movable into such cavity.

United States Patent Breakey et al.

[ Nov. 11, 1975 KNEE PROSTHESIS [75] Inventors: James W. Breakey, San Jose; John M. Freter, Santa Clara; Jack Wren, Dublin, all of Calif.

[73] Assignee: Hosmer/Dorrance Corporation,

Campbell, Calif.

[22] Filed: Feb. 10, 1975 [21] Appl. No.: 548,865

[52] US. Cl. 3/22 [51] Int. Cl. A61F l/04; A61F H08 [58] Field of Search 3/22-29, 2, 3/1

[56] References Cited UNITED STATES PATENTS 2.208.275 7/1940 McCann 3/22 X 2.666.208 l/l954 Funk 3/l X 3,316.558 5/1967 Mortensen..... 3/22 X 3,400,408 9/1968 Garcia 3/26 3,440,668 4/1969 Dachs et al. 3/l

Primary Examiner-Ronald L. Frinks Attorney, Agent, or Firml-larris Zimmerman [57] ABSTRACT A prosthetic device for the knee comprises a block which may be cast as a rigid, urethane member which closely resembles the appearance of the knee, and which includes an integrally formed resilient knee pad to serve as a shock absorber, to reduce pant leg wear, and to simplify the fabrication technique. The device is formed in a mold cavity by first pouring the knee pad material, such as pigmented resilient polyurethane, in the lower end thereof and allowing it to set. Rigid polyurethane material is then added and allowed to expand and fill the mold cavity, and to cure into a rigid state. The block is attachable to the lower end of an upper leg or femural prosthesis. A pigmented resin is used to form a laminate over the femural section and knee, using nylon and fiberglass as the matrix for the resin. The laminate fits flush with an annular shoulder extending from the knee pad. A knee prosthesis having a lightweight unitary construction, smooth continuous surface, realistic flesh tone exterior, and a similarly flesh-toned resilient knee pad is thus formed. In another embodiment of the insertion, the knee block includes a larger link cavity for attachment to a lower leg prosthesis, and the knee pad includes a flap portion movable into such cavity.

8 Claims, 7 Drawing Figures U.S. Patent N0v.11, 1975 Sheet1of2 3,918,103

Sheet 2 of 2 3,918,

US. Patent Nov. 11, 1975 FlG 5 1 KNEE PROSTHESIS BACKGROUND OF THE INVENTION The orthopedic art is replete with prosthetic knee devices of various descriptions and constructions. To generalize about these devices, it may be said that they involve an assemblage of parts which simulate the general size and function of a typical knee joint. This simulation is usually realistic only when the prosthesis is covered by a pant leg. The bare device can rarely be mistaken for a natural limb, either in coloring or configuration.

To provide the rigidity and durability required of a prothesis, the prior art devices are usually fabricated of hard substances such as wood or the like. Although i such materials provide excellent service, they cause extreme wear when rubbing on clothing fabric, and likewise cause overlying clothing .to be crushed when any impact occurs with a hard object or when the user is kneeling on a hard surface. This problem is most often encountered at the patella area of a knee prosthesis. To alleviate the problem, a pad may be provided, applied to the exterior of the prothesis and secured with standard methods such as screws, straps or the like. The effect of such an addition to the prosthesis is to reduce the likeness of the prosthesis to a natural knee joint, as well as causing maintenance problems.

SUMMARY OF THE INVENTION The present invention comprises a prosthetic device for the knee in the nature of a rigid urethane block which emulates the general shape of a natural knee, and is shaped to match the shade of the resin used to laminate the exterior of the prosthesis, and which also may generally match the skin tone of the wearer. The

knee prosthesis includes a pad formed of elastic cast polyurethane which minimizes the wear of the knee area of pants. The pad includes an annular flange extending outwardly from the edge thereof. A nylon and fiberglass coating is laminated to the rigid polyurethane, abutting the flange to form a smooth, continuous exterior surface. The coating may be toned to match the skin color of the wearer, so that the prosthesis closely approximates the appearance of a natural knee. It will be understood that the block could be formed of wood or other material, if desired.

THE DRAWING FIG. 1 is a vertical elevation of the prosthesis of the present invention. I

FIG. 2 is a vertical cross-sectional elevation of the prosthesis of the present invention.

FIG. 3 is a bottom view of the prosthesis of the present invention.

FIG. 4 is an enlarged, vertical cross-section of a por; tion of the prosthesis of the present invention.

FIG. 5 is a rear view of another embodiment of a knee prosthesis.

FIG. 6 is a vertical cross sectional view taken substantially in the plane indicated by line 6-6 of FIG. 5.

FIG. 7 is a bottom plane view of the structure shown in FIGS. 5 and 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention, as shown in FIGS. 1 through 4 of the drawings, comprises a prosthetic device for the knee and, in particular, is directed to a prosthesis for the lower femur region of the upper leg. The block-like prosthesis 10is adapted to be joined to the lower end of an upper leg prosthesis 11, as shown in FIG. 1. The prosthesis 10 generally comprises an upper portion 12 of a'truncated, tapering oval solid having a plane upper surface 13 and a plane lower surface 14 parallel thereto, and a lower pad portion 16 joined to the lower surface 14. The pad portion comprises an oval, convex disc formed of resilient material.

With reference to FIG. 2, the upper portion 12 is preferably cast of a rigid, lightweight substance such as polyurethane foam 17, but may be formed from wood, or other plastic, or the like. Such portion is provided with a centrally disposed cylindrical cavity 18 which serves to further decrease the weight of the prosthesis, andserves a function in attaching the prosthesis 10 to a depending socket on member 11 (not shown). The portion 12 is also provided with a vertically disposed rectangular slot or cavity 19 extending into the lower end of the portion 12 and perpendicular to the lower surface 14. A first hole 21 extends through the lower end of the portion 12, adjacent to the slot 19 and perpendicular thereto, and parallel to the lower surface 14. A second hole 22 extends through the portion 12, axially parallel to the hole 21, such holes being utilized as a pivot axisbetween the knee and lower leg prosthesis (not shown).

The lower "pad portion 16 is preferably cast of resilient polyurethane 23 or the like, integrally bonded to the upper portion. The pad portion 16 is provided with a circumferential configuration similar to that of the lower surface 14 The convex surface 28 of the pad portion extends beyond this circumferential surface 24, defining therebetween a laterally extending annular flange 26, as shown in FIG. 4 in detail.

Joined to the exterior of the prosthesis is a continuous exterior coating 27 of nylon laminate or the like, bonded to the exterior surface. The coating extends from the circumferential surface 24, where it abuts the flange 26 to form a continuous surface with the convex surface 28. From the flange the coating extends upwardly to the edges of the rectangular slot, covering the upper portion and extending beyond the upper surface 13 to join the prosthesis 10 to the adjacent leg prosthesis ll.

The coating may be provided with selected pigmentation to match the general skin tone of the wearer. With the general contours of a human knee and the continuous surface of flesh color, the prosthesis closely approximates the appearance of a human knee. The knee pad prevents damage to the prosthesis at the point of contact when the wearer is kneeling and avoids damage or undue wear to the pant leg of the wearer. Furthermore, the knee pad eliminates the necessity of providing a smooth lamination of nylon and resin at an area on the prosthesis over which it is difficult to do so.

It should be noted that the rectangular slot 19 is provided to receive the upper end of a mechanism (not shown) which provides controlled rate of motion about the knee hinge axis, while the hole 21 is adapted to receive therein a hinge pin. The hole 22 is adapted to receive a spring member which acts on the hinge to extend the joint of the prothesis. The mechanism, hinge pin, and spring form no part of the present invention.

A major feature of the present invention is the simplicity and economy of the method of fabricating the prosthesis. A mold is provided, having a cavity configured to the exterior of the upper and lower portion 13 and 14. Into this cavity the resilient, viscous, uncured polyurethane is poured. Before the polyurethane is cured, inserts to form holes 21 and 22, and the slot, are added, and the rigid polyurethane foam (in the reactive state) is poured on top of the resilient polyurethane, and the mold is capped as the foam reacts and fills the upper portion of the cavity.

After the urethane is cured, the durable nylon coat ing or laminate is applied, with a bonding agent such as a polyester resin or the like which is pigmented to match the skin color of the user. This coating may extend to bond the knee prosthesis to the upper prosthesis 11, or may form a socket at the upper end of the prosthesis to receive the member 11;

In FIGS. 5, 6, and 7, a modified form of knee prosthesis, generally denoted at 30, is provided. In distinction to the single axes knee 10, knee 30 has a larger slot or cavity 39 than slot 19 for the reception of links or the like. A pad portion 36 is joined to the lower surface 34 of the block, and such portion includes an oval portion 40 and a central flexible flap portion 42 having opposed edges 44, and a distal end 46 extending beyond the corresponding edge portion of the knee. The flap is movable to a position within the cavity 39, but normally extends outwardly and parallel to surface 34. The oval portion 40 has a laterally extending flange 48, similar to previously described flange 26 which serves as a stop for the subsequently applied laminate, not shown, and permitting the pad and the laminate to assume a flush continuous appearance.

We claim:

l. A prosthetic device for the knee, comprising a truncated, generally tapered, rigid, block portion of generally oval cross section, a knee pad portion adja- I cent the truncated surface of said rigid portion and integrally joined thereto, said knee pad portion formed of resilient material, and an exterior coating layer joined to the exterior surface of said rigid solid portion and from, and a convex face joined circumferentially to I said flange.

4. The prosthetic device of claim 3, wherein said exterior coating layer abuts said annular flange.

5. The. prosthetic device of claim 1, wherein said rigid, solid portion includes a rectangular slot extending therein normal to said truncated surface.

6. The prosthetic device of claim 1, wherein said rigid, solid portion is rigid synthetic foam and said pa portion is resilient synthetic foam. I

7. The prosthetic device of claim 1, wherein said knee pad portion includes a resilient tongue extending;

outwardly from said block portion.

8.,The device of claim 5, in which said knee pad portion includes a flexible tongue overlying said rectangular slot and generally parallel to said truncated surface. 

1. A prosthetic device for the knee, comprising a truncated, generally tapered, rigid, block portion of generally oval cross section, a knee pad portion adjacent the truncated surface of said rigid portion and integrally joined thereto, said knee pad portion formed of resilient material, and an exterior coating layer joined to the exterior surface of said rigid solid portion and abutting said knee pad portion.
 2. The prosthetic device of claim 1, wherein said knee pad portion includes a disk equal in circumferential configuration to said truncated surface.
 3. The prosthetic device of claim 2, wherein said disk includes an annular flange extending outwardly therefrom, and a convex face joined circumferentially to said flange.
 4. The prosthetic device of claim 3, wherein said exterior coating layer abuts said annular flange.
 5. The prosthetic device of claim 1, wherein said rigid, solid portion includes a rectangular slot extending therein normal to said truncated surface.
 6. The prosthetic device of claim 1, wherein said rigid, solid portion is rigid synthetic foam and said pad portion is resilient synthetic foam.
 7. The prosthetic device of claim 1, wherein said knee pad portion includes a resilient tongue extending outwardly from said block portion.
 8. The device of claim 5, in which said knee pad portion includes a flexible tongue overlying said rectangular slot and generally parallel to said truncated surface. 